1. Field of the Invention
This invention relates to an image shake compensating device for an optical monitoring apparatus, an optical instrument such as a still camera or the like.
2. Description of the Related Art
Image shake compensating devices of varied kinds have recently been proposed for still cameras. Still cameras equipped with such devices are being developed.
The known image shake compensating devices are generally arranged to include a shake detector which detects a shaking state (acceleration, speed of displacement) of an optical instrument such as a camera; a compensating optical system which is movable in the direction of offsetting an image shake resulting from shaking of the optical instrument in such a way as to prevent any image shake on the image forming plane of the optical instrument; a computing device for computing a degree of shake compensation to be made by the compensating optical system on the basis of the output of the shake detector; an actuator which drives the compensating optical system on the basis of the output of the computing device; a servo detector which detects the moving extent and the position of the compensating optical system; and a compensating optical system driving control device for driving the actuator on the basis of a difference between the output of the computing device and the output of the servo detector. The control system of the conventional image shake compensating device is as shown in a block diagram in FIG. 24 of the accompanying drawings. In FIG. 24, a compensating optical system moving degree detector represents the above-stated servo detector.
The conventional image shake compensating device which includes the above-stated control system necessitates the optical instrument to use the shake detector which detects shaking of the optical instrument and the compensating optical system moving degree detector which detects the moving degree of the compensating optical system. This requirement not only increases the size of the instrument but also requires use of a complex electronic circuit arrangement for complex control. This causes an increase in cost of the image shake compensating device and eventually in cost of the instrument.